source: vendor/perl/5.8.8/djgpp/fixpmain

#!perl -w
# Fix perlmain.c under DOS (short & case insensitive filenames).
# Called from Makefile.aperl when needed.
# You don't need this when LFN=y.

use Config;

open (PERLM,"<perlmain.c") or die "Can't load perlmain.c: $!";
open (MAKEFILE,"<makefile.pl") or die "Can't load makefile.pl: $!";
undef $/;
$perlmain=<PERLM>;
$makefile=<MAKEFILE>;

($_) = $makefile =~ /\bNAME\b.*=>\W*([\w\:]+)/; # extract module name
$badname=join ("__",map {lc substr ($_,0,8)} split /:+/); # dosify
$perlmain =~ s/^.*boot_$badname.*$//gm if $badname; # delete bad lines

@exts=('DynaLoader',split (" ",$Config{known_extensions}));
for $realname (@exts)
{
    $dosname=join ("__",map {lc substr ($_,0,8)} split /\//,$realname);
    $realname =~ s!/!__!g;
    $perlmain =~ s/\bboot_$dosname\b/boot_$realname/gm;
    $dosname =~ s/__/::/;
    $realname =~ s/__/::/;
    $perlmain =~ s/\b$dosname(::bootstrap)/$realname$1/gm;
}

#DynaLoader is special
$perlmain =~ s/(DynaLoader:\:boot)strap/$1_DynaLoader/gm;

open (PERLM,">perlmain.c") or die "Can't write perlmain.c: $!";
print PERLM $perlmain;